[47.03] Direct Analysis of Spectra of the Type~Ia Supernova 1994D

K. Hatano, D. Branch, E. Baron (U. Oklahoma)

SN~1994D, in the Virgo cluster galaxy NGC 4526, is the best
observed Type~Ia supernova. We use the parameterized
supernova synthetic--spectrum code SYNOW to make a direct
analysis of observed spectra of SN~1994D throughout its
photospheric phase. The synthetic spectra match the observed
spectra in considerable detail. We find evidence from the
spectra that the temperature at the photosphere increased
from about 11 to 4 days before maximum light, and then began
to decrease, in accord with the behavior of the broad--band
colors of SN~1994D, and we see evidence in the spectra for
the expected conversion of radioactive nickel to cobalt and
then iron. We establish constraints on the composition
structure of the ejected matter (composition versus ejection
velocity). For example, sulfur and magnesium were confined
to rather narrow velocity intervals similar to those of the
unmixed carbon deflagration model W7. Spectra obtained well
before maximum light show evidence for carbon moving as
slowly as 12,000 km s-1, in contrast to the minimum
carbon velocity of 26,000 km s-1 that we found
previously for the Type~Ia SN~1990N. These and our other
constraints can be used to restrict the range of
hydrodynamical models that could represent SN~1994D.